Biggest bang would be the Oregon cams 2106 (easy), Dutra RV10RDP (hard if Doug lost his stock in the fire) and the Dutra duals with the pipes run back at least behind the transmission cross member before the collector back into one pipe (much harder). Easier if willing to go to a mini starter but I am on a mission to make this work. Make sure you time the cam.
View attachment 1715633145 View attachment 1715633146 View attachment 1715633147